1. Field of the Invention
The present invention relates to a lens module and an electronic apparatus, and particularly to a lens module having a function of moving an optical element forward and backward along the optical axis direction when electric power is applied and an electronic apparatus including a body housing to which the lens module is attached.
2. Description of the Related Art
Some cameras to be built in mobile phones and other electronic apparatus do not have an autofocus (AF) function. A camera of this type is called a fixed-focus camera and includes a lever that switches the focus position by using, for example, a cam structure between the focus position corresponding to a standard imaging mode and the focus position corresponding to a macro-imaging mode, which is, for example, used in barcode recognition. A user uses the lever to move a lens holder manually in the optical axis direction (see JP-A-2006-276200, JP-A-2006-039480, JP-A-2005-352287, JP-A-2005-300606, and JP-A-2005-157290, for example).
In a manual switching camera of this type, the user sometimes set the lens to the position corresponding to infinity by mistake in the macro-imaging mode. To solve the problem, it is necessary to provide a complicated control system (see JP-A-2008-072465, for example). Further, since the switch for the switching purpose is exposed to the outside, it is difficult to make the switch waterproof, and implementation of the switch is limited in terms of area and location, which may require a precise implementation technology (see JP-A-2007-074583, for example).
An ion-conducting polymer actuator has been proposed as a next-generation actuator that not only replaces the manual lens driving described above with electrically powered lens driving but also satisfies the demands on a camera module built in a mobile phone, such as size reduction, power saving, cost reduction, and easy assembling (see Japanese Patent No. 2,768,869, for example).
An ion-conducting polymer actuator is formed of a cation-exchanged cation exchange film containing water and electrodes joined with both surfaces of the ion exchange film. Alternatively, an ion-conducting polymer actuator is formed of a water-containing ion exchange film, electrodes joined with both surfaces of the ion exchange film, and a polymer material coated on the ion exchange film and the electrodes. In operation, applying a potential difference across the ion exchange film causes the cation exchange film or the polymer material coating to bend or deform and hence operate as an actuator.
In recent years, lens holder driving mechanisms using an ion-conducting polymer actuator of the type described above in a camera module to be built in a mobile phone or any other mobile apparatus have been proposed. Camera modules having a similar configuration have also been proposed. (See JP-A-2006-301202, JP-A-2007-206362, JP-A-2007-139862, and JP-A-2007-097259, for example).